Dewatering of fibrous materials



Sept. 29, 1942.

DEWATERING OF FIBROUS MATERIALS Filed March 17, 1959 ITBILLJNG D- R-U'OHNSTON f HVVCNTOFSS A TTOHNEYS J. BILLING ETAL V 2,296,897

Patented Sept. 29, 1942 UNITED STATE nswa'rsnme or FnmoUs MATERIAL Joseph Billing and David Robert Johnston, Spondon, near Derby, England, asslgnors to Celanese Corporation of America, a corporation of Delaware I Application March 17, 1939, Serial No. 262,512

In Great Britain April-5,1938

4 Claims.

This invention relates to a method for dewatering and/or cleansing fibrous materials, which is especially applicable to the dewatering and cleansing of wood pulp and other short'fibre forms of cellulose, and to apparatus for carrying out the method.

The methods commonly employed in dewatering long staple cotton and similar long fibre forms of cellulose cannot be used satisfactorily with short fibre cellulose such, for example, as linters or wood pulp. It is an object of the present invention to provide a method and means for dewatering and at the same time cleansingv short fibre forms of cellulose.-

According to the invention the cellulose or other fibrous material is formed into a web reor supported web is passed through one or more squeezing presses. Preferably the web is passed through a series of squeezing presses, by means of which it is subjected to gradually increasing pressures.

As the strings there may with advantage be used cotton or other spindle cord. of say or A" to outside diameter, and the strings may, for example, be spaced 1 to 6 inches apart. In order to diminish the tendency to breakage due\ to uneven strain it is-advisable to employ twoor multi-plycords and to knot each ply separately, preferably with reef knots, the positions of the knots being staggered so as to provide as even a contour as possible.

The function of the strings is to aid in preserving the structure of the web, whether ornot in any particular instance the web is sufllciently strong, without the help of the strings, to pass through the dewatering device without breaking or disintegrating. Thus they may'act to supinforced by moving strings, and the reinforced port an otherwise unstable web or to strengthen further a web which is already moderately strong, and both these functions are included under the word reinforce" as used in the pres- -ent specification and claims.

, The web is preferably formedon adewatering One rubber covered rollers, may be positioned against the dewatering roll, so that the web passes b tween them and the dewatering roll. From the dewatering roll the web, reinforced by the strings, may be carried between a series of pairs of rubber'rollers each exerting a greater pressure than its predecessor. For example three or more such pairs of rollers may be rollers there maybe employed two or more heavy roller presses, for example spring presses, again each exerting a higher pressure than the last. The pressures exerted by the rollers may be adjusted according to the degree of dryness desired in the final product.

In order to remove the cellulose or other fibrous material from the strings the web may then be passed over a heater roll or similar device which releases the material, which may then be delivered to any desired subsequent treatment.

After the removal of the material the strings may be returned directly to-the dewatering roll.

In another method of applying the invention pecially directly before passing through the last heavy press, be transferred from the initial set of strings to another set of strings. This may be done by passing the web over a roll round which both sets of strings pass, the strings of each set being arranged alternately. One advantage of transferring the material from one set of strings to another before passing it through the last press is that, after passing through the'last press, it can be removed from the strings without the use of a heater roll or similar device, thus saving wear due to the heater. Another advantage is that when only two heavy presses are used, the possibility that between the presses the strings may be strained owing to slight irregularities in the drive or in the thickness of the web is avoided. v 1

Not only does the new process provide a very eflicient way of dewatering short fibre as well as long fibre cellulose, and producing a substantially dry coherent sheet therefrom, .but it is found that when applied to short fibre cellulose it results in a purer product than has hitherto been obtained. Apparently the free and even removal of the water causes fine particles of foreign matter, for example sand and hard residues of non-cellulosic substances, to be washed out from the cellulose; a

If desired a yet purer produce may be obtained by washing the web before it passes through each or any of the presses. For example the web may be sprayed with a suitable washing medium.

Thus for instance a 'web comprising short fibre cellulose may be sprayed with water before it enters any one or more of the presses. I

Although the new process is of great value in drying short-fibre cellulose, it may also be used for drying other typesof fibrous material. Thus it may be employed for dewatering staple fibres used. Following these of silk or wool, or of cellulose derivatives such for instance ascellulose acetate. Moreover it treated, sprays 43 may be provided before the can be applied in the dewatering of inorganic fibrous material, for instance asbestos.

Apparatus embodying the invention is illustrated in the accompanying drawing, in which Fig. 1 shows diagrammatically in vertical seconto the dewatering roll I and formed into a web. Rubber-covered rolls [2 are positioned above the dewatering roll It) so as to apply increasing pressures to the web, which then passes in succession through two pairs of rubber-covered rolls. l3, wherein it is subjected to yet higher pressures, and through two heavy spring-loaded presses. l4 and I5, which are adjustable according to the degree of dryness desiredvs In the form of apparatus illustrated in Figs. 1 and 2 there are two sets of strings 30' and 3|. The first set 30 passes between the dewatering roll I!) and the first heavy press I4; the second set 3| passes through the second heavy press l5. Between the presses l4 and I5 are three guide rolls 32, 33, 34. Both sets of strings pass Over the guide roll 32, strings from the two sets lying alternately. The first set of strings 30 then passes round the guide roll 33 to a guide roll 35 and guide comb 36 back to the dewatering roll ID; the second set 3| passes over the guide roll 34, through the second press I5 and thence overuide rolls 3'! and 38; from the roll 38 the strings return underneath their former path through a guide comb 39, over a driving roll 40 and over guide rolls 4|, 42 back to the guide roll 32. A hopper 25 is positioned below the guide roll 38.

In the illustrated apparatus, .the guide rolls 32, 33, 34, 35, 31, 38, 4| and 42 are freely rotatapairs of rolls I 3.

Having described our invention, what we desire to secure by Letters Patent is:

1. A device for dewatering or cleansing and dewatering fibrous materials, which comprises a rotatable dewatering roll, a guide roll, two squeezing presses disposed on opposite sides of said guide roll and horizontally spaced with respect to each other, two sets of endless parallel strings, and means including the dewatering roll and a positively driven roll for driving said strings, onev set of strings passing around the dewatering roll, through one squeezing press and around said guide roll, and the other set passing around said guide roll and through the other squeezing press, the second set of strings cooperating with the first set at said guide roll to take up from said first set the fiber web formed thereon at the dewatering roll and carry it forward through the second squeezing press:

2. A device for dewatering or cleansing and dewatering fibrous materials, which comprises a rotatable dewatering roll, a guide roll, two squeezing presses disposed on opposite sides of said guide roll and horizontally spaced with respect to each other, two sets of endless parallel strings, and means including the dewatering roll and'a positively driven roll for driving said strings, one

set of strings passing around the dewatering roll, through one squeezing press and around said guide roll, and the other set passing around said guide roll and through the other squeezing press, the second set of strings alternating with the first set of strings during their passage around said guide roll and cooperating with the first set at said guide roll to take up from said set the iiber web formed thereon at the dewatering roll and carry it forward through the second squeezing 'press. I

3. A device according to claim 2 wherein the strings are twoor multi-pl'y, each ply being knotted separately and the knots staggered along the lengths of the string.-

4. A device according to claim 2 which is'provided with means for applying a washing medium on to the material about to pass through one or more of the squeezing presses.

JOSEPH BILLING. DAVID -ROBERT JOHNSTON. 

